The owner is very helpful. After knowing that I am ripped off by the taxi driver, he immediately called the taxi driver up (the taxi driver called him to get the directions before that). However, the taxi driver refuse to give a refund. The next morning, he is still v angry about it and offered to make a report. I agreed to that but I have to leave for jeju that day so he still continue to follow up and on the same day, the taxi driver agreed to refund the excess amount charged. He told me that he did this because he doesn't want me to have a bad impression of korea. What a nice host!
The location of the guesthouse is superb! It's 22mins away from incheon airport via AREX and 15mins away from Gimpo airport.